ABSTRACT
This chapter reviews on the usefulness of pH-sensitive liposomes for the delivery of oligonucleotides without residence time within lysosomes. The effect of divalent cations may be an important parameter to take into account in the design of pH-sensitive liposomes. In fact, in cells the factors that control drug transfer by those vectors are still poorly understood; cytoplasmic delivery by these pH-sensitive liposomes appears incomplete. About half of the total cell-associated pH-sensitive immunoliposomes delivered their content into the target cell cytoplasm. The use of pH-sensitive liposomes in therapeutics would require that vehicles remain stable in the circulation until binding and subsequent endocytosis by target cells. The goal would be the production of antigen-specific, pH-sensitive liposomes that combine access to target cells in tissues and the efficient delivery of liposome contents in the cytoplasm. The requirement for acid sensitivity in the design was demonstrated when pH-insensitive immunoliposomes did not mediate efficient transfection.
